With the objective of improving the system efficiency and providing a homogenous coverage, the wireless communication networks envision the deployment of multiple-input multiple-output (MIMO) systems, full frequency reuse, and a denser deployment of transmitters. In such scenario, efficient interference management techniques are expected to play a crucial role in improving the transmission data rates.
The MIMO interfering channel is a generic model for cellular communication systems, in which a plurality of transmitters, each equipped with multiple antennas, wish to send independent messages to their intended receiver while generating interference to all remaining receivers. Unfortunately, the optimal transmit/receive strategy with linear spatial filters that maximize the weighted sum of data rates of the system is not known because of the non-convexity of the problem.
Already existing centralized interference management approaches allow finding locally optimal solutions, but they require of a central unit to collect the Channel State Information (CSI) of all receivers, and further the complexity of the solution scales with the number of transmitters times number of receivers. For those reasons, most current research focuses on decentralized techniques. Recent decentralized procedures consider the exchange of control-plane messages among transmitters to convey the degradation of the data rate due to the created interference (also called interference prices). This knowledge allows to control the interference at the transmitters by selecting the transmit power and the linear transmit precoder. On the other hand, the maximization of the weighted sum of data rates can be obtained by iteratively minimizing the weighted sum of Mean Square Errors (MSEs) [Christensen-08][Shi-11], where the error weighting matrices are chosen accordingly to the inherent relation between the data rate and the Minimum MSE (MMSE).
Nevertheless, all these decentralized procedures require the interfering channels be estimated and reported by the receivers to interfering transmitters. Hence, channel estimation errors on the interfering links and the overhead associated to the reporting of channel gains have a detrimental effect on the overall potential gains.
Other solutions proposed in the field are detailed in the patent documents below. They are mainly focused on wireless cellular communication systems, where transmitters are Base Stations (BSs) and receivers are User Equipments (UEs). The downlink (DL) transmission is understood as the transmission from BSs to UEs, and the uplink (UL) transmission as the transmission from UEs to BSs.                U.S. Pat. No. 6,718,184, incorporated by reference herein, describes a linear precoding technique for an antenna array at the BS that is able to balance the coverage and the generated interference towards other cells by studying the quotient between the DL received power at the desired in-cell UE and the DL power at the other-cells UE. To that end, they estimate the covariance matrix of the desired signal and the covariance matrix of the interfered UEs using UL transmissions. The procedure is not able to guarantee a certain SINR or link quality to the UEs.        EP-A-2045930, incorporated by reference herein, discloses a method for decentralized yet iterative power control in a network of nodes with the target of guaranteeing a certain CA. Convergence of the method is proved. The method exploits Time Division Duplex (TDD) access mode and hence channel reciprocity, but it is not applicable to a multi-antenna transmission system.        U.S. Pat. No. 8,023,955, incorporated by reference herein, enables decentralized schedulers by exploiting the reciprocity of radio channels in TDD or Frequency Division Duplex (FDD) systems by preemptively controlling inter-cell interference levels in the downlink transmission. It applies for the interference control in the UL transmission.        WO-A-2010/148371, incorporated by reference herein, provides inter-cell interference coordination in femtocell networks where the UE determines the information from interfering cells and reports this information to them either directly or indirectly through a backhaul link. The information reported by the UE is used for beamforming design so as to mitigate the interference in the direction of said UE. Communication among cells is required.        EP-A-2045930, incorporated by reference herein, describes methods for inter-cell interference coordination using resource partitioning in which UEs are allocated to orthogonal time or frequency resources. WO-A-2010/148371 discloses methods and apparatus for beamforming for femtocells, such as in LTE wireless networks, to provide inter-cell coordination and interference mitigation based on a macrocell UE obtaining information regarding an interfering Home evolved Node B (HeNB) and the HeNB may adjust an output based on the information.        U.S. Pat. No. 8,023,855 divulges a computer program for performing a method of inter-cell control by allocating uplink transmission resources in a mobile station of a wireless communication system where a figure of merit for transmission to the BS is calculated for adjusting an uplink transmission resource parameter at the UE.        WO-A-2011/088465, incorporated by reference herein, reveals a method for interference mitigation in a wireless communication system where interference information including an amount of uplink interference experienced at a BS or serving cell is determined (comparing the interference value to a target value) and scheduling signal transmission is performed within the serving cell based at least in part upon the interference information.        EP-B-2045930, incorporated by reference herein, discloses a method for communicating between a transceiver apparatus and a communication partner in repetitive radio frames wherein the step of transmitting during the transmission time slot of the second radio frame comprises transmitting the second transmit signal with the second transmission power being dependent on the interference power and a control component.        U.S. Pat. No. 8,401,480, incorporated by reference herein, refers to a method for transmitting feedback information at a UE in a wireless communication system that performs a Coordinated Multi-Point (CoMP) operation, comprising measuring noise and interference variances corresponding to a signal strength or an interference level using reference signals received from one or more neighbor BSs.        U.S. Pat. No. 8,260,206, incorporated by reference herein, reveals a method for uplink and downlink inter-cell interference coordination (ICIC) by a HeNB where a data exchange with a UE is performed, a measurement report is received and transmit power is reduced with a first slew rate and increased with a second slew rate.        WO-A-2011/055943, incorporated by reference herein, discloses a method for UL transmission control in a wireless communication system including the steps of receiving from a first UE information on a frequency band having an UL interference occurring therein with respect to a second BS and allocating an UL resource for the first UE based upon the frequency band.        